A digital video broadcasting (DVB) receiver receives incoming signals from a selected source, such as a broadcast source, e.g., terrestrial or other such source. After tuning to a desired channel, incoming data is demodulated to obtain signal information, such as in accordance with a given MPEG standard. Oftentimes, the data is modulated using orthogonal frequency division multiplexing (OFDM). Typically, a receiver includes a front end including a tuner section, which receives and tunes to a desired channel. The incoming signal is then converted to a digital data stream, which is provided to a demodulator. Oftentimes, the demodulator output is provided to forward error correction (FEC) circuitry to handle errors present in the data stream. The data stream provided by the demodulator to the FEC circuitry can be quite jittered because of the structure of the OFDM symbol in the frequency and time domains.
In the frequency domain, synchronization and signalization carriers are regularly spread in between data carriers, and null carriers are put on the edges of the fast Fourier transform (FFT) window so that the spectrum remains in the available channel bandwidth. In the time domain, the guard interval creates a temporal burst, which could last up to a quarter of the OFDM symbol total duration. In addition, time synchronization might also involve sudden jumps of the FFT window start signal due to apparition or disappearing of echoes. These jumps can practically range between +/− guard interval duration. As a result, the total guard interval duration between OFDM symbols becomes dynamic, ranging from zero to up to twice the guard interval.
Despite this variation, the output data stream provided from the demodulator to other receiver circuitry such as an audio-video decoder, should have minimal jitter. Some systems provide for byte rate smoothing at a rear end of FEC circuitry. This requires additional hardware and raises complexity of processing. Specifically, an extra memory is needed at the backend of the FEC circuitry to absorb all prior bursts related to demodulation parameters and synchronization. As described above, such bursts can last up to twice the guard interval time period, and this additional memory consumes additional chip real estate. Furthermore, the entire FEC circuitry suffers from this jitter prior to this output-based byte rate smoothing.
Other known techniques provide for static data stream smoothing. However, such static jitter correction is implemented typically for a worst case scenario. Under this type of correction, there is always a gap to absorb, particularly when the guard interval is relatively large with respect to the number of FFT demodulator carriers. Furthermore, under dynamic channel conditions such as apparition of a pre-echo, part of the data carriers may be temporarily lost, causing a burst of erroneous packets at the output of the FEC circuitry.